The present invention relates to a method for fixing an annular element onto a shaft and a shaft assembly obtained by such method. The shaft may be, for example, a camshaft and the annular element may be, for example, a cam piece or a journal piece used in an automobile.
In automobiles, many camshafts are produced by means of sintering, in which, at first, a preliminarily sintered cam piece or journal piece is fixed onto a shaft temporarily before being permanently fixed as a result of the completion of sintering. In such an operation, it is necessary that the temporarily fixed cam piece be anchored to the shaft so that it is not displaced relative to the shaft either in the axial direction or in the rotating direction. For this purpose, conventional assembling of a camshaft assembly of the above-described type has been carried out according to the following method comprising the steps of: forming an axially extending groove on an outer wall of the shaft and forming an axially extending projection on an inner surface of a through hole of the piece, the groove and projection having respective cross sections which enable them to fit tightly together; inserting the shaft into the through hole of the piece while engaging the projection tightly with the groove, thereby securing the piece to the shaft temporarily before permanently fixing it onto the shaft as a result of completion of sintering.
However, the above method is disadvantageous in that there is an unavoidable dimensional variance between the groove and the projection. If the variance is large, the projection is loosely fitted to the groove, resulting in a reduction of holding capacity between the two elements; on the other hand, if the projection is fitted too tightly to the groove, breakage of the projection and groove results.